The introduction of optical fibres in the field of communication and the need for very large scale integration within the integrated circuits industry together with recent developments leading towards the fabrication of novel electronic devices has created a demand for thin epitaxial films of compound semiconductors. Some of these are the binarys GaAs, and InP, the ternarys CdHgTe, GaInAs, GaAlAs and GaInP and the quaternarys like GaInAsP. Growth of thin epitaxial films of these and other compound semiconductors is presently been carried out by various techniques such as liquid phase epitaxy (LPE) Molecular beam epitaxy (MBE) and chemical vapour deposition (CVD).
Deposition from the vapour phase is in most cases the preferred technique since it can be conveniently scaled-up to grow on large area substrates, including growth on multiple substrates. Also it offers maximum control of material properties such as thickness and composition. Another practical advantage is that it does not involve the contacting of the growing surface with a liquid or solid phase thus avoiding numerous potential problems during and after the growth process.
However the production of device quality films of compound semiconductors demands achieving uniformity of composition, crystal structure and electrical properties during growth. In addition the commercial viability of fabricated devices based on compound semiconductors depends on the reproducible availability of such films.
In the growth of reproducible, reliable and effective films the growth environment is as important as the process being used i.e. there is a key link between the growth environment and the growing film. The degree of effective homogeneity in terms of reactant partial pressures, temperatures and contact times largely determines the quality of the film produced. It is this parameter of the growth process that the present method is designed to aid significantly. The method enhances the degree of homogeneity by utilising a highly efficient means of intermixing high purity reactants within processing constraints while maintaining the integrity of the high purity reactants. At the same time the method developed provides additional features which are essential for the reproducible growth of high quality films.